Posted
by
timothy
on Tuesday April 12, 2011 @09:02PM
from the when-montana-and-wyoming-indicate-scale dept.

jd writes "Really big. By using electrical conductivity tests rather than seismic waves, geologists have remapped the Yellowstone caldera. Whilst seismic waves indicate differences in the reflectivity of different materials, it doesn't show everything and contrast isn't always great. By looking at the electrical conductivity instead, different characteristics of molten and semi-molten rock can be measured and observed. The result — the caldera is far larger than had previously been suspected. This doesn't alter the chances of an eruption, and it's not even clear it would change the scale (prior eruptions are very easy to study, as they're on the surface) but it certainly changes the dynamics and our understanding of this fierce supervolcano."

The Yellowstone eruption [wikimedia.org] was a little smaller than Toba (2500 km^3 as opposed to 2800 km^3) but you probably don't notice after the first thousand cubic kilometers of ash have landed. There are four other supervolcanos known [wikimedia.org]. Certainly these are extinction-level events - the Year Without A Summer was caused by a tiny volcano in comparison, altering global temperatures a mere 0.4'C, but the levels of famine and disease that resulted were staggering. Scale it up a hundredfold and throw in a continent's worth of ash and you're talking major problems for anything on the surface.

The one in the summary is fine, but the original (better) article is here:http://www.unews.utah.edu/p/?r=032411-5 [utah.edu]It talks more in depth about how they actually did the imaging. It's actually quite interesting.